Field of Invention
The present invention relates generally to advanced control and advanced manufacture, specifically to a computer-aided numerical control method and system for a new generation of control-machines. The present invention is used to manufacture related data flow file, thereby completely realized the software implementation for R&D (Research and Development) of computer numerical control technology and reconfiguration of computer numerical control system, so as to create an open platform for R&D of computer numerical control technology and computer numerical control system. The related data flow file, as a computer program product, will be commercializing digital control information (numerical control information), and then will be expediting a new industry namely digital control information manufacture.
Description of Related Arts
Ever since 1952 MIT developed the first electronic tube numerical control system, after times of transistors, integrated circuits, minicomputers and microcomputers, the computer numerical control (CNC) is developed into PC-based open architecture control (OAC) in the eighties of the last century, which has three modes: PC embedded in NC, NC embedded in PC, and soft-open.
The OAC is considered to be the key technology of high-performance and intelligent control. NC embedded PC mode, i.e. an open numerical control system based on motion controller is the mainstream of existing open numerical control systems, motion controllers has became a high-tech industries and swept the world. An open motion controller is known as the new generation of industrial controllers in the United States, and is considered to be the future of a third industrial revolution in Japan.
In a general sense, the architecture of the modern manufacturing system can be abstracted into three systems, namely power-machine, work-machine and control-machine. The power-machine provides energy, the control-machine sends control information to the power-machine and the work-machine, and the work-machine manufacture products.
A sign of a first industrial revolution was birth of the work-machine, machinery instead of hand tools.
A sign of a second industrial revolution was birth of the power-machine, such as a steam engine, internal-combustion engine, and motor, instead of humans and animals.
The third industrial revolution will be birth of a control-machine, as a main indicator.
From a manufacturing industry point of view, the above division is logical.
In a manufacture system, the CNC system plays the role of the control-machine. However, because there exist serious defects in openness, reconfiguration, standardization, and software implementation of numerical control technologies, the existing CNC system is not compared with the power-machine and the work-machine, and is difficult to become the control-machine that is expected for the third industrial revolution.
The “Technical Committee of Open Systems” of IEEE defines an open system as follows: “An open system provides capabilities that enable property implemented applications to run on a variety of platforms from multiple vendors, interoperate with other system applications and present a consistent style of interaction with the user” (IEEE 1003.0).
The Chinese National Standard “GB/T 18759.1-2002 mechanical and electrical equipment•open CNC systems—Part 1: General Principles•3.1” seizes the nature of the IEEE definition and follows its basic principle, the openness is straightforwardly defined as “plug-and-play” of application software, its definition of the open CNC systems is as follows: “An open CNC system runs on a system platform constructed according to the principles such as the publicity, scalability and compatibility, and possess the portability, interoperability and consistency of human-machine interface.”
The IEEE-definition shows that the IEEE defines a CNC system as a special purpose-computer system. Therefore, the architecture of the open CNC systems is divided into two categories, i.e. a system platform and an application software platform. It is the architecture oriented application software. Therefore, the application software is divided into the man-machine control level and the motion control level. The motion control level is used to execute a real-time control process, and inextricably to link with a specific iterative interpolation control algorithm, which is a kernel of the CNC system.
As a result, under the leading of the IEEE-definition, operation rules in iterative interpolation, algorithms are tightly coupled together with task schedule rules in a real-time operating system, it forms a real-time CNC method namely the iterative interpolation method.
The iterative interpolation control method runs through the entire history of the numerical control method and system, and create the “the interpolation era” of the existing CNC systems.
The basic technical solution of the iterative interpolation control method is as follows. The method is based on a real-time operating system. The time-sharing cycle in the real-time operating system is an interpolation period. For a given tool-path and feedrate (F), by using an iterative interpolation algorithm, the digital control information concerning relevant axes is real-time calculated, and is in real-time sent to motion control systems (step-type motion control system or servo-type motion control system) that is used to control a deterministic motion relationship in a mechanical system. The digital control information includes discrete position information concerning relevant axes, and associated information between the discrete position information.
As is known, when solving multi-axes increments for a tool-path, an interpolation algorithm is an iterative algorithm in the numerical calculation. The so-called iterative interpolation algorithm, in essence, is to obtain a set of operation rules on Xn+1 from Xn. Because of function continuity, Xn certainly imply some information on Xn+1. To fully use of these informations can be simplified a high-order complex operation into a low-order simple operation, and led to greatly improve the speed of the iterative interpolation algorithm. So as to avoid high-order complex operations, some optimal iterative interpolation algorithms cannot be adopted. On the other hand, to obtain operation rules on Xn+1 from Xn, in general, is too difficult for some complex tool-paths. Therefore, an iterative interpolation algorithm with the high-speed and high-precision becomes the core of existing CNC method.
The present invention discovered that the iterative interpolation control method has the following four essential characteristics.
1. In order to improve a feedrate (F), the existing open CNC systems must be use time-divided method.
For a straight-line of the length of L, according to the feedrate (F) and the interpolation period (T), the time-divided method must be discrete the straight-line into some line-segments ΔLi:ΣΔLi=L, ΔLi=FT.
As is known, for the straight-line, as long as given F, the machining task can be completed. However, because the interpolation period lead to real-time iteration, the above formula shows that the linear interpolation had to be discrete the straight-line into many line-segments.
For the circular interpolation, the time-divided method first uses a number of line-segments to approximate a curve: Δ Li=FT, which is called a rough interpolation, and then a fine interpolation. The formula: er=(TF)2/(8r) gives the relationship between the discrete error (er), the federate (F), the interpolation period (T), and curvature radius (r).
The formula also pointed out that er is proportional to the square of F and T, and is inversely proportional to r. The growth of F and/or T lead to exponential growth of er, in other words, er is highly sensitive to the time, the feedrate and the curvature.
Therefore, for the iterative interpolation control method, time was locked by the interpolation period, and is no longer a controllable external free variable, but a uncontrollable internal system parameter.
This is the first essential characteristic of the iterative interpolated control method, and is also its endogenous basic defect.
2. In the interpolation period, on the one hand, the iterative interpolation algorithm generates digital control information, which immediately are in real-time sent to the motion control system to drive the corresponding axes. On the other hand, the digital control information, as the input in next interpolation period, are in real-time feed backed to generate next digital control information. This is a real-time iteration of digital control information.
To follow beats of the interpolation period, the digital control information are generated, sent and executed periodically, so again and again. This is a real-time iteration of control process.
Therefore, through the real-time iterations of digital control information and control process (denoted by I&P real-time iteration), the overall manufacturing process of the digital control information is real-time.
This is the second essential characteristic of the iterative interpolated control method, and is also its endogenous basic defect.
3. The I&P real-time iteration is a centralized control mode based on real-time operating system. For this control mode, “have absolute control on major issues, grasp at authority on minor ones, carry right down to the grass roots level”, the real-time operating system command all, plan, design, and construction are at the same time.
This is the third essential characteristic of the iterative interpolated control method, and is also its endogenous basic defect.
4. The discrete error er is inversely proportional to r, and is proportional to the square of F and T. However, a workpiece-contour is only a geometry problem, so a tool-path, er and r are also a geometry problem. F of the tool center is only a problem concerning the machining process and kinematics and/or dynamics of the electromechanical system.
The iterative interpolation control method tightly coupled together such as er, r, T, and F, i.e. space, time, velocity, acceleration/deceleration, and even jerk. This means that the iterative interpolation algorithm is strongly correlative with the geometry structure of a tool-path, hereby the geometry characteristics of the tool-path, the characteristics of the machining process, and the kinematics/dynamics characteristics of the mechanical system all tightly coupled together. The coupling relationship between the time and the space of a tool-path can be simply called as the time-space coupleness.
This is the fourth essential characteristic of the iterative interpolated control method, and is also its endogenous basic defect.
The present invention found that the IEEE-definition produced the following five serious deviations, and misled development direction of the CNC method and the CNC system.
1). The Existing CNC Systems are Computerized by the IEEE-Definition
From a historical point of view of development of the computer and its applications, the multi-task operating system was an epoch-making progress, which is used to time-sharing run programs of many users. However, in essence, the multi-task operating system just provides a management mechanism for internal/external resources and an adjustment mechanism for internal/external environmental changes.
Under the leading of the IEEE-definition, the iterative interpolation control method developed the management mechanism and the adjustment mechanism in the real-time operating system as a universal control mechanism. The real-time operating system has become a real-time control center to be used in real-time to generate the digital control information through the iterative interpolation algorithm, further the architecture of the existing CNC system is based the real-time operating system. It is lead to the overall CNC application software becoming a large and complex interrupt system. Thus, the existing CNC system is completely “computerized”, and became a special-purpose computer system needed to arrange a real-time operating system.
2). The IEEE-Definition Produced a Series of Pseudo-Problems, Hereby LED to the Complexity of the Existing CNC Method and CNC System
The existing CNC systems are fully computerized by a real-time operating system. The many technical problems became key problems, such as interpolation-speed and interpolation-precision of the iterative interpolation algorithm, multi-axes linkage, real-time forward-look control of F, acceleration/deceleration control, high-speed pretreatment of CNC programs, cross-coupling control, etc. The above technical problems are completely pseudo-problems, which are produced by the above four endogenous basic defect of the iterative interpolation control method, thereby artificially led to the complexity of the existing CNC method and system.
3). The IEEE-Definition Reinforces the Real-Time of the Overall Control Process
In the CNC system, the so-called real-time means that some real-time tasks have strict requirement in terms of the time, hence these tasks must be implemented in the predictable time. The real-time is the premise to implement real-time control, the interpolation-speed of the iterative interpolation algorithm is an important condition for control stability. The iterative interpolation algorithm is a core to generate control information in real-time, in essence, its interpolation-speed and interpolation-precision determine the overall system performance and reliability.
For the work-machine (in the present invention, simply, the work-machine includes the power-machine and its motion control system), the real-time control task is to send the discrete position information on relevant axes into the motion control systems by F, so that the movements of relevant axes are used to implement compositive displacements.
Under the leading of the IEEE-definition, the iterative interpolation control method uses a centralized control mode of “planning, design, and construction are at the same time”. The overall manufacturing process of the digital control information is a real-time through the I&P real-time iteration, therefore the real-time of the control process is reinforced.
4). The IEEE-Definition Hindered the Standardization of the Prior CNC Systems
The open architecture is considered to be the key technology of high-performance and intelligent control. In the natural sciences, unlike a closed system (also known as a conservative system), an open system is that its matter, energy and information exchange with the external environment.
In the computer field, the basic meaning of the openness is plug and play of application software.
However, the openness is a concept in the humanistic field only sensed but not spoken. More importantly, the CNC is a process, not an object. The openness of a process is completely different with the openness of an object. Therefore, in the CNC field, for nearly three decades, the content on the openness has not been able to be uniformed and regulated.
As is well known, the standardization of parts and components is the lifeline of modern manufacturing. The CNC systems are complex systems composed of many subsystems, which are also complex systems. For a machine, a part or component is similar with a sub-system, and can even be said that a subsystem is a “part” of the complex system. In a CNC system, if subsystems and interfaces therebetween are standardized, and have interchangeability, obviously, then the CNC system is open.
In the engineering field, the aim, effect, and methods of the openness and standardization are very close. The standardization necessarily implies the simplicity in means of the use, maintenance, and user's secondary development.
Energy and matter is a commodity, information is also a commodity. The main aim of the openness and standardization is to obtain the liquidity in the commodity significance for the digital control information.
For CNC, the basic content of the openness is the standardization in means of the digital control information, digital control information manufacturing process and internal interface in the process. The architecture of the CNC system, its hardware and software resources are necessary to meet the needs of large-scale industrial production in the information industry, and to provide standardized control-machines for work-machines and power-machines.
It can be seen, during the development process of information manufacturing, to adapt the standardization of work-machines and power-machines, the development of the manufacturing environment requires to standardize digital control information and CNC systems, that embodies the openness of the CNC system. The essence of the openness is that the manufacturing system of digital control information can be changed from a rigid system to a flexible system. It is necessary to lead the standardizations in means of the digital control information, digital control information manufacturing process and internal interface in the process.
As a result, the present invention defined the CNC system openness as: the openness of CNC system is the standardization of CNC system in the flexible course, i.e. the standardization of the digital control information, the process to manufacture digital control information, and the internal interface in the process.
From the foregoing definition it can be clearly seen, the so-called openness is a problem of how to realize the standardizations of the digital control information, the process to manufacture digital control information, and the CNC system. This definition is expected, but also fully understood, not ambiguous, by the manufacturing industry. This definition laid an open operable platform, and also pointed out the direction for how to realize standardization of CNC system.
Under the lead of the IEEE definition, the existing CNC systems were computerized, the openness is limited to “plug and play” of the application software. It completely ignored the technical features of CNC in the overall control process, and led to the prior CNC system's loss of the proper direction, and further hindered the standardization course of CNC systems.
5). The IEEE-Definition Misled the Development Direction of CNC Technologies
The iterative interpolation algorithm with high-speed and high-precision is the core technology in the existing CNC systems. Therefore, the OSEC (Open System Environment for Controller) project in Japan thought that an open CNC system without advanced control algorithms is only evolutionary, not ideal and revolutionary.
So-called algorithm, briefly said, is a method computer-based to solve some problems. The ACM defines computer science as fellow: computer science researches the process of algorithm to describe and transform information. Algorithms and their implementation process are the foundation of computer science.
The iterative interpolation control method led to the development of CNC to advanced iterative interpolation algorithms, it is bound to concern in the core of computer science.
From an information theory point of view, the CNC system is only used to decompress the digital control information compressed in a tool-path and F.
Under the control of a real-time operating system, the iterative interpolation control method, as a decompression method for digital control information, is real-time. The core of the real-time operating system is the process/thread scheduling. The real-time led to complicate the process/thread scheduling. Parallel algorithm led further to complicate the process/thread scheduling. As compared with the pipeline concurrency at instruction-level and process scheduling concurrency at processor-level, the uncertainty resulted from the thread concurrency is extremely complex.
The task scheduling of a real-time operating system seriously restricts the performance of the overall system. In order to implement a very complex process/thread scheduling, the CNC software goes deep into the real-time operating system's front fields such as multi-process and/or multi-thread multi-nested calls and real-time multi-nested interrupts. Therefore, speed and precision of the iterative interpolation control algorithms become the key technical indicators of the existing CNC systems.
The problem is that if F of the work-machine is improved, or the movement precision is improved, and the number of linkaged-axes and/or the linkaged-parameters is increased, then the interpolation period is longer exponentially. It requires a CPU with more bits and higher speed, a real-time operating system with more bits and more hard the real-time, and a more advanced iterative interpolation algorithm.
Therefore, on the one hand, the operation rules in iterative interpolation algorithms and the task scheduling rules in real-time operating systems are coupled tightly in real-time together by the IEEE-definition, the development direction of CNC technology is led to forefront fields in the algorithm theory and the operating system. On the other hand, CNC technology and chip technology are bundled together by the IEEE-definition, this means that developments of the existing CNC technology depend on CPU's speed, in another word, in essence on chip technology.
The inventor invented the data flow related control (DRC) method in the patent “A data flow related control method and architecture for computer numerical control system” (ZL 2007 1 0124304.9, date of grant: Aug. 19, 2009), the existing CNC systems have bid farewell to the interpolation era, and have strided into the DRC era. A control-machine, i.e. the DRC-based control-machine was born.
In the CNC field, “1”/“0”-type discrete position information are widely used. However, in many cases, discrete position information are not “1”/“0”-type, but to increments. A related data flow with “1”/“0”-type discrete position information commonly is called as the step-type related data flow, and then a related data flow with increments is called as the increment-type related data flow.
TABLE 1t1t2. . .ti. . .tnΔX1: 1ΔX2: 1. . .ΔXi: 1. . .ΔXn: 1Δy1: 0Δy2: 1. . .Δyii: 0. . .Δyn: 1ΔZ1: 1ΔZ2: 0. . .ΔZi: 1. . .ΔZn: 0ΔA1: 1ΔA2: 0. . .ΔAi: 0. . .ΔAn: 1ΔB1: 1ΔB2: 1. . .ΔBi: 1. . .ΔBn: 0
The Table 1 is a 5-linkaged step-type related data flow of a tool-path with 5 axes, the tool-path is a function of variables X, y, Z, A, B, where time T is discreted into n time points: ti (i=1, . . . , n), the value is “1” at each ti for the axis(X), and is “1” or “0” at each ti for the other four-axes.
Thus, the digital control information consists of two parts. The first part is discrete position information such “1” or “0” as for five-axes(X, y, Z, A, B) at each time point ti, and the linkageness therebetween, which are used to produce synthetic displacements. The second part is the followness between the synthetic displacements, i.e. time intervals between the adjacent synthetic displacements, which are used to determine F.
TABLE 2t1t2. . .ti. . .tnΔX1: 1ΔX2: 1. . .ΔXi: 1. . .ΔXn: 1Δy1: 0Δy2: 1. . .Δyii: 0. . .Δyn: 1ΔZ1: 1ΔZ2: 0. . .ΔZi: 1. . .ΔZn: 0ΔA1: 1ΔA2: 0. . .ΔAi: 0. . .ΔAn: 1ΔB1: 1ΔB2: 1. . .ΔBi: 1. . .ΔBn: 0W1W2. . .Wi. . .WnE1E2. . .Ei. . .EnH1H2. . .Hi. . .Hn
The Table 2 is a 8-linkaged step-type related data flow with 3 parameters (for example, W is the width 0f the laser pulse, E is the energy of the laser pulse, H is the frequency 0f the laser pulse) and the five axes, where the values of W, E, H are different by real-time control at ti.
TABLE 3Δt1Δt2. . .Δti. . .ΔtnΔX1ΔX2. . .ΔXi. . .ΔXnΔy1Δy2. . .Δyi. . .ΔynΔZ1ΔZ2. . .ΔZi. . .ΔZnΔA1ΔA2. . .ΔAi. . .ΔAnΔB1ΔB2. . .ΔBi. . .ΔBnΔW1ΔW2. . .ΔWi. . .ΔWnΔE1ΔE2. . .ΔEi. . .ΔEnΔH1ΔH2. . .ΔHi. . .ΔHn
The Table 3 is a 8-linkaged increment-type related data flow with 5 axes and 3 parameters, the tool-path is a function of variables X, y, Z, A, B, where T is discreted into the n intervals: Δti (i=1, . . . , n); ΔXi, Δyi, ΔZi, ΔAi, ΔBi are increments of X, y, Z, A, B; ΔWi, ΔEi, ΔHi are parameter changes of W, E, H during Δti (i=1, . . . , n).
Thus, the digital control information consists of two parts. The one is increment information concerning the relevant axes and/or virtual axes and linkageness therebetween, that is the L-division ΔLi(i=1, . . . , n) that is used in real-time to control the synthetic displacements and to produce five-axes linkage, and in real-time to control parameter-changes during Δti. The other is Δti and the followness between the adjacent synthetic displacements, that is the T-division Δti(i=1, . . . , n). For a curve, the L-division is a increment-type related data flow which is a sequence of consecutive micro-segments which maximum normal distance from the tool path is less than or equal to a discrete scale.
IT can be seen clearly from the foregoing Tables, the basic problem of CNC is to manufacture the related data flow.
For the increment-type related data flow, the first basic problem is how to plan the micro-segments ΔLi in the L-division ΔLi (i=1, . . . , n) according a given discrete error and optimization goals, and to control the relevant axes to move their increments during Δti, and to composite the micro-segment ΔLi, briefly, that is to solve the linkageness of the L-division.
The second basic problem is how to control F of the relevant axes during Δti, and to determine the T-division, briefly, that is to solve the followness of the L-division.
For DRC, the linkageness of the L-division concerns only in the increments of relevant axes. This is different from the iterative interpolation control method. The linkageness of the L-division is purely a discrete geometry problem, which is independent of the discrete algorithm and/or interpolation algorithm, and the discrete process to generate the increment-type related data flow. The followness of L-division concerns in F and kinematics/dynamical characteristics of the axes, in essence, it is independent of geometry structure of tool-path.
For DRC, the manufacturing process of the related data flow is a non-real-time planning process, therefore is independent of real-time operating system. This is different from the iterative interpolation control method.
Obviously, compared with the step-type related data flow, to manufacture the increment-type related data flow is much more complex. On the one hand, it is to optimizate the L-division ΔLi (i=1, . . . , n), which is called the discrete geometry planning; on the other hand, it is to optimize the T-division Δti (i=1, . . . , n) concerning the axis smoothness, which is called the discrete kinematics planning.
Therefore, by means computer-aided, the discrete geometry planning and the discrete kinematics planning to be used to manufacture the increment-type related data flow is the primary task for the DRC-based control-machine.